Re: How can I make a spk simulator load


"John Stewart"
> Phil Allison wrote:
>
>> >
>> > About a year & half ago I built a Loud Speaker Simulator very much like
>> > that shown in Phil's article. For the input L I have a 90 microhenry
>> > aircore
>> > choke followed by a 7.5R, 10 watt resistor. The low freqency resonance
>> > is formed
>> > by a Mallory 220 microfarad NP motor starting cap in parallel with a
>> > Hammond
>> > 159ZC choke ( 60 mh, 0.7R).
>> >
>>
>> ** Such a low value for the input L means you are effectively simulating
>> a
>> speaker that has a copper cap ( inductance damper) on the pole piece -
>> ie
>> as is commonly used for wide range or twin cone speakers.
>>
>> The bass resonance is at 44 Hz but the peak current before saturation is
>> only 2 amps for the 159ZC, so power input is a bit limited.
>
>
>
> The rise of impedance caused by the 90 microhenry choke starts at about
> 4KHz &
> is well up at 10 KHz, similar to a real speaker.


** As usual, you are totally wrong.

Your circuit only rises to 9.4 ohms at 10 kHz while typical woofers have
inductance figures of 0.5 to 2.5 mH - depending on coil size. The impedance
at 10 kHz is 20 to 30 ohms, unless a copper shorting ring or pole cap is
fitted.

Then the figures are like your circuit.




......... Phil


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